Numerous processes are known for the preparation of toner particles, such as, for example, conventional processes wherein a resin is melt kneaded or extruded with a pigment, micronized, and pulverized to provide the toner particles. The toner particles may also be produced by emulsion aggregation (EA) methods. Methods of preparing EA type toner particles are within the purview of those skilled in the art, and toner particles may be formed by aggregating a colorant with a latex polymer formed by emulsion polymerization.
Toner systems normally fall into two classes: two component systems, in which the developer material includes magnetic carrier granules having toner particles adhering triboelectrically thereto; and single component systems, which generally use only toner. In single component development systems, both magnetic and non-magnetic systems are known.
Placing charge on toner particles, to enable movement and development of images via electric fields, is often accomplished with triboelectricity. Triboelectric charging may occur either by mixing the toner with larger carrier beads in a two component development system or by rubbing the toner between a blade and donor roll in a single component system.
With non-magnetic single component development (SCD), the toner may be supplied from a toner house to a supply roll and then to a development roll. The toner may be charged while it passes a charging/metering blade. Non-magnetic SCD toner requires high flowability and high chargeability because the time for toner to flow through the contacting nip formed between the blade and the development roll is very short. Low charge causes reduced solid area development, increased toner dusting in white areas of the page (background), and/or poor development stability over time.
Another issue with SCD systems is toner robustness. The high stress under the blade may cause the toner to stick to the blade or the development roll. This may reduce the toner charge and the toner flowability. Since non-magnetic toner is charged through a charging/metering blade, low charging and low flowability may cause print defects such as ghosting, white bands, low toner density on images, and/or background development.
Surface additives having round shape particles are commonly used during the preparation of conventional toner particles for the purpose of reducing surface forces and improving the toner's flow. Examples of common surface additives may be, for example, round shaped titanium dioxide and silica carbide.
There remains a need for a toner composition suitable for high speed printing, particularly high speed printing that may provide excellent flow, stability, charging, and improved photoreceptor cleaning in a non-magnetic single component development system.